Relationship between Ground Displacement and Gas Pipeline Damage According to InSAR Analysis of Palsar-2 Imagery

The distribution of ground displacement due to the 2016 Kumamoto earthquake was obtained from the analysis of the synthetic aperture radar (SAR) satellite image and the relationship with damage to the low-pressure gas distribution pipes was investigated. First, we estimated the co-seismic ground displacement with an accuracy of approximately 0.04 m by differential interferometric SAR (D-InSAR) analysis of the PALSAR-2 imagery on the ALOS-2 satellite which observed the affected area before and after the earthquake. Then, we calculated the displacement of the quasi-east-west and the quasi-vertical directions from the combination of two line-of-sight (LOS) displacements estimated from two pair images with different observation conditions and examined the relation with damage ratios of gas distribution pipes. As the results, a correlation between the gradient of the ground displacement and the damage ratio was found and the damage ratio tended to increase as the gradient became larger.